1. Field of the Invention
The present invention relates to a liquid crystal display device, and more specifically, to a micro-transflective liquid crystal display device with improved reflectivity.
2. Description of the Prior Art
Since the advantages of a liquid crystal display (LCD) device over a conventional CRT monitor include better portability, lower power consumption and lower radiation, the LCD device is widely used in various portable products, such as notebooks, personal data assistants (PDA), electronic toys, etc.
The LCD device is a passive luminous device, so that a supplemental light source is usually required to generate light beams when the LCD device displays images. In general, the LCD devices can be classified into reflective LCD devices, transmissive LCD devices and transflective LCD devices. A transmissive LCD device usually has a backlight module for generating light beams, which pass through a liquid crystal element and various optical elements such as polarizer for allowing users to see images displayed by the transmissive LCD device. However, when the intensity of ambient light beams is too high, display quality of the transmissive LCD device is degraded. Therefore, in order to solve the above-mentioned drawbacks, a micro-transflective LCD device is developed by adding a reflective element in the transmissive LCD device for reflecting the ambient light beams. Additionally, a reflective LCD device includes a reflective surface (such as aluminum) therein. Light beams such as ambient light beams enter the reflective LCD device from the front of the reflective LCD device, pass through a liquid crystal element and various optical elements, and are reflected by the reflective surface. Then, the reflected light beams pass through the liquid crystal element and the optical elements again such that users can see images displayed by the reflective LCD device. In addition, a transflective LCD device has characteristics of both the transmissive LCD device and the reflective LCD device. When intensity of the ambient light beams is high enough or the transflective LCD device requires fewer light beams to display images, the transflective LCD device reflects ambient light beams to display images. Additionally, when intensity of the ambient light beams is quite low or the transflective LCD device requires more light beams to display images, a backlight module in the transflective LCD device is switched on to generate light beams. Therefore, the transflective LCD device has an advantage of reducing power consumption of the backlight module.
Generally, reducing power consumption is major development of a portable electronic product such as a mobile phone, which is equipped with a LCD device. Hence, the transflective LCD device is usually applied in the portable electronic products because it has an advantage of low power consumption. Taking a mobile phone as an example, images displayed on a LCD device of the mobile phone usually include time or messages showing missed calls when the mobile phone is in a standby mode, and it does not require high intensity of light beams to display those images on the LCD device. Therefore, the LCD device of the mobile phone can reflect ambient light beams to display images when the mobile phone is in a standby mode. Additionally, a backlight module in the LCD device is switched on to generate light beams so that a user can clearly see images such as numerals or characters displayed on the LCD device when the mobile phone is in a use mode.
Generally, there are three kinds of transflective LCD devices or micro-transflective LCD devices that are briefly described as follows. The first one involves adding a reflective layer in a panel of a LCD device as disclosed in U.S. Pat. No. 6,493,051. However, since at least an extra thin-film deposition process and an extra photolithographic process are required in manufacturing such kind of LCD device, production cost is increased and the probability of forming defects may be raised owing to the higher amount of manufacturing processes, thereby reducing yield. The second one involves forming a reflective layer in a polarizer of a LCD device as disclosed in U.S. Pat. No. 6,018,419, but such kind of LCD device has disadvantage of a high production cost and complex manufacturing processes. The third one involves modifying patterns of a light-guiding plate of a backlight module and using a reflective plate of the backlight module to reflect ambient light beams. Nevertheless, portions of the ambient light beams will be lost in the light-guiding plate, thereby decreasing reflectivity of the ambient light beams and reducing brightness of images displayed on the LCD device.